1. Field of the Invention
The present invention concerns a device for maintaining the speed of an aircraft within a speed range (operational range) delimited by the maximal speed and the minimal speed authorized by the technical capabilities of said aircraft, regardless of the flight path commanded.
It will be noted that the invention applies more particularly to an aircraft, especially a commercial aircraft, having control means for applying to said aircraft a commanded rate of climb and a commanded speed, based on received control values.
2. Description of the Prior Art
In the manner that is known in itself, said control means are incorporated:
either in the automatic pilot of the aircraft, which is capable of operating: PA1 or in the flight director which indicates to the pilot the movements to be applied to the pitch axis control to obtain the required flight path. PA1 either manually, by the pilot, by appropriate movement of the throttle control; PA1 or automatically, by means of an automatic thrust control system. PA1 firstly, if for a positive imposed rate of climb, i.e. one which corresponds to the aircraft climbing, the speed produced by the maximal thrust that can be generated by the propulsion system falls below the prescribed minimal speed; and PA1 secondly, if for a negative imposed rate of climb, i.e. one which corresponds to the aircraft descending, the speed produced by the minimal thrust rises above the prescribed maximal speed. PA1 duplication of protection is necessary at each protected decision center; and, more importantly PA1 the extent of protection is limited to the field of application of the corresponding decision center with its own authority, in particular when the aircraft is in cruise mode, which can lead to a large and highly prejudicial excursion of the speed of the aircraft out of the range delimited by the authorized minimal and maximal speeds. PA1 control means for applying a controlled rate of climb to said aircraft; PA1 means for determining the effective speed of said aircraft; PA1 means for comparing said effective speed with said maximal and minimal speeds, respectively; PA1 means for calculating, on the basis of said comparison, two modified control values adapted to align said effective speed with said maximal and minimal speeds, respectively, by modification of said rate of climb; and PA1 priority action means for imposing on said control means one of said modified control values if such action is necessary to maintain the speed of said aircraft within said speed range. PA1 the rate of pitch of the aircraft; PA1 the longitudinal attitude of the aircraft; or PA1 the load factor, which corresponds to the difference between the vertical acceleration of the aircraft and the acceleration due to gravity. PA1 a first calculator unit which determines from said effective speed and from said maximal speed a first control value corresponding to the value of said reference parameter for which said aircraft may be brought to said maximal speed; PA1 a second calculator unit which determines from said effective speed and from said minimal speed a second control value corresponding to the value of said reference parameter for which said aircraft may be brought to said minimal speed; PA1 a third calculator unit which determines from the effective rate of climb of said aircraft a third control value corresponding to the value of said reference parameter for which said aircraft may be brought to a zero rate of climb; PA1 a first selector unit which chooses either said first control value or said third control value as said first modified control value, according to which of them produces the greater nose-down attitude of said aircraft; and PA1 a second selector unit which chooses either said second control value or said third control value as said second modified control value, according to which of them produces the greater nose-up attitude of said aircraft. PA1 said first and second load factor control values are advantageously respectively proportional to the differences between said effective speed and said maximal and minimal speeds, respectively, and PA1 said load factor third control value is advantageously proportional to the effective rate of climb of the aircraft.
directly through appropriate control units known in themselves on control surfaces of the aircraft to modify its rate of climb; and PA2 indirectly on the propulsion system to modify the thrust; the speed of the aircraft is the result of the rate of climb/thrust combination;
Consequently, the use of an automatic pilot completely automates the control of speed and rate of climb, whereas the use of a flight director necessitates the intervention of the pilot.
Despite these differences, and although the present description refers first and foremost to an automatic pilot, the invention applies equally well to an aircraft provided with an automatic pilot and to an aircraft provided with a flight director.
For a rate of climb of the aircraft corresponding to an imposed control value, maintaining the speed of the aircraft at a prescribed value is effected, in a manner that is known in itself, by controlling the thrust generated by the propulsion system of said aircraft, such control being effected:
Under the above conditions, maintaining the speed in the operational range is impossible in the following situations:
To remedy these critical situations, the automatic pilot includes internal protection devices incorporated in localized decision centers relating to the various possible modes of operation of the aircraft which either limit the control values imposed on the automatic pilot or modify the mode of operation so that the imposed rate of climb is compatible with the prescribed maximal and minimal reference speeds.
These internal protection devices have many drawbacks, however, including:
An object of the present invention is to remedy these drawbacks. The present invention concerns a device for automatically maintaining the speed of an aircraft, in particular of a commercial aircraft, within a speed range delimited by minimal and maximal speeds authorized by the technical capabilities of said aircraft.